Characterization of a New Transposon, Tn, on a -Carrying Plasmid From Multidrug-Resistant ssp. in China.

Background: is an opportunistic pathogen which is responsible for serious nosocomial infections. A gene which plays an important role in resistance to carbapenems is the New Delhi metallo-β-lactamase 1 (NDM-1). Currently, the spread of NDM-1-producing strains is a serious public threat.

Methods: A multidrug-resistant ssp. strain CBG15936 was recovered in 2017 in Guangzhou, China. PCR, S1-pulsed-field gel electrophoresis, and Southern blotting were performed to locate the gene. Susceptibility testing and conjugation experiments were also performed. Illumina HiSeq and Nanopore sequencers were used to perform whole-genome sequencing.

Results: Strain CBG15936 belongs to ST932 and is resistant to carbapenems. The gene was found on a ∼62-kb plasmid, which has a conjugation frequency of 1.68 × 10 events per donor cell. Genome sequencing and analysis revealed that the NDM-1-carrying IncN1 plasmid contained a new transposon Tn, which consists of an intact -carrying Tn element, an inverted 8.3-kb Tn remnant, IS, Δ, and IS.

Conclusion: A new transposon, Tn, has been detected on a -carrying plasmid recovered from multidrug-resistant ssp. CBG15936 from China. This finding provides a new perspective regarding the potential for to undergo horizontal transfer among drug-resistant bacteria.